In the manufacture of semiconductor devices, silicon wafers are typically employed. These silicon wafers must be coated with photoresist. To enhance adhesion of the photoresist to the silicon wafer, the wafer must first be primed with HMDS (hexamethyldisilazane).
There are three known techniques for applying HMDS to the silicon wafer. In accordance with one prior art technique, HMDS in a liquid form is simply applied directly to the wafer as it is spun. Because this stream technique is typically performed in an open environment, the silicon wafer is exposed to water vapor in the atmosphere. The water vapor has a detrimental affect on the adhesion of the photoresist to the wafer.
In an effort to avoid exposing the silicon wafer to water vapor during the priming process, another technique involves heating the silicon wafer to evaporate any water which is present thereon and exposing the wafer to HMDS vapor, which condenses onto the wafer. However, the water vapor present in the chamber still has a detrimental affect on the priming process.
In an effort to expose the silicon wafer to as little water vapor as possible, yet another technique involves placing batches of wafers in a heated vacuum chamber. One problem with such a batch priming technique is that it does not lend itself to production line automation, whereby the wafer is subjected to successive processing operations without operator interface.